Does the meaning of the sentence below change by adding a comma? If so, could someone explain the grammar. All I know is that in the second sentence the phrase "like a rockstar" would be considered a nonessential part of the clause. Does the punctuation influence the meaning of the sentence in any way?
"She was pretty like a rockstar."
"She was pretty, like a rockstar."
"She was pretty like a rockstar."
"She was pretty, like a rockstar."